Implement CSI Volume Cloning Feature

[pmonday]

The initial version of the driver does not implement volume cloning (https://v1-20.docs.kubernetes.io/docs/concepts/storage/volume-pvc-datasource/).

This should be achievable by

• creating a snapshot of the PVC referenced
• create the clone
• export the clone as a file system or LUN

This issue is 'generic' and may be split up if the filesystem path is substantially different from iscsi. For now, filesystem would be the priority since it would be common for boot images and home directories and such.